Former HSBC banker Simon Birkett has spent the past five years pressuring the government to improve air quality in London. Photograph: Frank Baron for the Guardian

Simon Birkett is fighting for air – of the clean variety. The 51-year-old former banker has spent the past five years campaigning against poor air quality and what he describes as the "biggest public health failing or cover-ups in modern history".

He is waiting to see whether the government has obtained a delay to comply with a key air-quality law on dangerous particles, known as PM10s, which will allow it to avoid up to £300m in fines. He wants the request to be turned down to give the UK a "wake-up call" over what many believe is a serious public health issue.

Methodical research, tireless lobbying and questioning, and freedom of information requests have left him with the impression that the government "seems willing to do or say anything except actually get on and tackle the problem".

Last year, monitoring equipment in the City of London repeatedly recorded dangerous levels of minute airborne particles, giving the city the unenviable reputation as one of the most polluted in Europe . "It is time that the London mayor and the so-called greenest government realise that compliance with health-based air-quality laws is not an optional extra," he says.

Although he voted Conservative at the last general election, Birkett says his campaign is non-party political. He heaps most of the blame for the UK's pollution problems on the former Labour government, which he says failed to tackle the problem adequately. However, he is also less than impressed with the coalition's efforts, and accuses Boris Johnson, the London mayor, of taking "backward steps" on the issue.

"It is time to say enough is enough and show a willingness to act," he says. "If instead of saying air quality is fine and it only takes six months off your life, people were saying actually it takes up to 11 years off your life, that it is worse than smoking and reduces the lung size of kids living near a very busy road by 15%, I reckon you'd have the public clamouring for action."

Birkett found his campaigning legs relatively late in life, while working in the senior echelons of HSBC. The Australia-born, privately schooled son of a civil engineer and foreign office secretary worked in several posts at the bank over 21 years, but his last three were spent juggling the day job with campaigning. In 2009 he took early retirement to devote his time to the fight against pollution.

He says he puts in 50 to 60 hours a week, relies on his modest pension and savings, and admits to having learned his campaigning skills on the job. He has become more media savvy over the years and uses Twitter and a regularly updated website to get his message across.

The former banker says his campaign style is neither aggressive nor passive, but "that middle road where you just keep making your point". His accountability is to the network of supporters signed up to his campaign, among them borough councillors and several members of the London assembly.

His efforts in pressuring the government for official figures on premature deaths are, by his own reckoning, his biggest achievement.

It was a chance article in a local newspaper in 2006 that alerted Birkett to the poor quality of air breathed in by Londoners. He had been serving on the Knightsbridge residents' association, in west London, and was engaged in a lengthy battle with Westminster council against rat-running in local streets.

He discovered there were powerful laws in Europe to protect the public from heavy air pollution, which were being breached in the UK. "I thought if these public laws were complied with then we would achieve most of the aims we wanted – less traffic, quieter roads, better quality of life, health and less noise," he says.

As late as 2010 the only official government estimates available suggested about 8,000 people had died prematurely in 2005 because of short-term exposure to PM10s emitted by industry, traffic and domestic heating. Some 1,000 of those hailed from Greater London.

In 2009, the European Environment Agency published figures suggesting those figures were almost three times higher. Birkett wasted no time writing to the then health secretary, Alan Johnson, urging him to publish the true scale of the problem – but no answer came.

He submitted evidence to the House of Commons environmental audit committee, whose subsequent report concluded that poor air quality made asthma worse, exacerbated heart disease and respiratory illness and "probably causes more mortality and morbidity than passive smoking, road traffic accidents or obesity".

Living in a pollution hot spot could shave up to nine years off the lives of the most vulnerable, the cross-party panel of MPs found. They urged the Department of Environment, Food and Rural Affairs to make air quality a higher priority and release the latest figures on premature deaths.

An official nationwide estimate was published by the committee on the medical effects of air pollutants shortly after, which showed that 29,000 premature deaths in the UK in 2008 were attributable to long-term exposure to PM2.5 – even smaller particles. It also found the particles, combined with other factors, might have contributed to the early deaths of up to 200,000 people.

Birkett's sights are now on the time extension for PM10 daily limit values. Thanks to London, the UK is still in breach of the European commission directive five years on and has had its first bid for an extension turned down. If the latest one is refused, the UK is likely to be referred to the European court of justice, which could impose hefty fines.

His frustrations with the Labour government over its failure to act has been compounded by the Tory-led coalition, which he believes attempted to "mislead" the European commission in September on the scale of the breaches.

He is dismayed that the government is blocking a freedom of information request he lodged two years ago, and disappointed that the Liberal Democrats' manifesto promise to work towards full compliance with air-quality laws by 2012 has become a pledge only to work towards it.

Birkett – whose tireless anti-pollution efforts were rewarded with the City of London Corporation's sustainable city award for air quality this month – has no plans to quit the campaign trail. "There is a long way to go," he says. "I'll stop either when we've actually met the objectives, which is the World Health Organisation standards, or if somebody else took it on." For now, he seems the right man for the job.

Sign up for the Guardian Today

Our editors' picks for the day's top news and commentary delivered to your inbox each morning.